JP4353554B2 - Laser light irradiation device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a laser beam irradiation apparatus that can uniformly irradiate a laser beam.
[0002]
[Prior art]
In recent years, polycrystalline silicon (hereinafter referred to as “p-Si”) is used as a semiconductor layer in place of amorphous silicon (hereinafter referred to as “a-Si”) which has been widely used until now. A liquid crystal display (Liquid Crystal Display, hereinafter referred to as “LCD”) has been developed. Laser annealing using laser light is employed to form or grow the p-Si crystal grains.
[0003]
FIG. 7 is a conceptual diagram showing a configuration of a laser beam irradiation apparatus for performing laser annealing.
[0004]
In the figure, 1 is a laser beam oscillation source, 2 and 11 are reflection mirrors, 3, 4, 5, and 6 are cylindrical lenses, 7, 8, 9, 12, and 13 are condensing lenses, and 10 is a linear laser beam. A slit 14 in the minor axis direction is a stage that supports the substrate 20 to be processed having a-Si formed on the surface.
[0005]
The laser light oscillated from the laser light oscillation source 1 is divided by the cylindrical lenses 3, 5, and 4, respectively in the vertical (long axis) and left and right (short axis) directions. This laser beam is converged in one direction by lenses 8, 9, 12, and 13 as shown in FIG. 8, and is stretched in one other direction by lens 7 as shown in FIG. Into a laser beam. Then, the substrate 20 is irradiated with this linear laser beam. The stage 14 on which the substrate 20 to be processed is placed is scanned in the short axis direction of the linear laser light, and high-throughput laser annealing by large area processing can be realized.
[0006]
[Problems to be solved by the invention]
FIG. 10 shows the intensity of the laser beam having a width of Ws in the minor axis direction of the linear laser beam.
[0007]
In the figure, the horizontal axis indicates the position of the laser beam in the short axis direction, and the vertical axis indicates the intensity of the laser beam at each position of the linear laser beam.
[0008]
As shown in the figure, in the width Ws (for example, about 400 micrometers) in the minor axis direction, the strength varies depending on the position, and is not uniform in the regions a and b at both ends. Therefore, since the laser beam irradiation is not performed sufficiently and uniformly, when the laser beam is irradiated at a location where the intensity is low, the crystal grain size of the polycrystallized p-Si at that location is not sufficiently large. It exists in the film in a microcrystalline state. The film in the microcrystalline state remains in the microcrystalline state because the crystallization does not progress further even when laser light irradiation is performed again with sufficient intensity, and the particle size cannot be increased. The crystal grain size will vary.
[0009]
For example, as shown in FIG. 11, the linear laser beam shown in FIG. 10 is equivalent to one LCD panel 31 of 95 × 130 mm on the substrate 20 to be processed using the laser beam irradiation apparatus shown in FIG. 7. The mother glass substrate 30 including nine substrates to be scanned is scanned with the linear laser beams 32 and 33 (illustrated by arrows in the right direction in the figure) to irradiate the entire surface uniformly, but once irradiated with weak intensity. In this region, the silicon layer is formed as a microcrystalline silicon layer, and even if the weak intensity region is irradiated again with laser light, the microcrystalline silicon remains as it is without increasing its grain size. That is, in one scanning of linear laser light, a silicon layer made of microcrystalline grains is formed in a band shape along a portion where the scanning intensity of the linear laser light is weak.
[0010]
As described above, the TFT made of p-Si, which can obtain only low mobility because the polycrystallization is not sufficiently performed, cannot obtain a sufficient ON current. For this reason, when the portion where the intensity of the laser beam irradiation is weak hits the pixel portion, there is a problem that the ON current of the TFT in that region is lower than in other regions and the contrast ratio is lowered. In addition, when the portion where the intensity of the laser beam is weak hits the peripheral drive circuit portion around the pixel portion, the ON resistance of the TFT increases, the operation speed decreases, and a malfunction occurs. In particular, a large-screen, high-definition LCD has a large number of pixels, so the writing time to the pixels is shortened, and the pulse width in the peripheral drive circuit section is also shortened. It becomes.
[0011]
Similarly, as shown in FIG. 12, also in the width W1 of the linear laser beam in the major axis direction, the intensity of the laser beam varies depending on the position in the major axis direction as in the minor axis direction. In the regions a and b, the intensity distribution is lowered, and there is a disadvantage that the crystal grain size of p-Si is not uniform.
[0012]
Therefore, the present invention has been made in view of the above-described conventional drawbacks, and an object of the present invention is to provide a laser beam irradiation apparatus capable of sufficiently and uniformly irradiating a linear laser beam on the entire surface of an object to be irradiated.
[0013]
[Means for Solving the Problems]
The laser beam irradiation apparatus of the present invention includes a laser beam oscillation source, a plurality of lenses that linearize laser beam by combining laser beams emitted from the oscillation source, and the irradiated object of the linear laser beam, A linear laser beam emitted from a plurality of lenses is collected, and a light diffusing plate is provided between the laser beam irradiated object and the nearest focusing lens.
[0014]
In addition, a slit for blocking the end of the linear laser beam in the long axis direction is provided between the condenser lens and the laser beam irradiated body.
[0015]
Furthermore, the size of the opening of the slit is variable.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a conceptual diagram showing a configuration of a laser beam irradiation apparatus according to an embodiment of the present invention. In the figure, 1 is a laser beam oscillation source, 2 and 11 are reflection mirrors, 3, 4, 5, and 6 are cylindrical lenses, 7, 8, 9, 12, and 13 are condensing lenses, and 10 is a linear laser beam. A slit 14 in the short axis direction is a stage that supports the substrate 20 to be processed. A diffusion plate 40 that diffuses linear laser light is provided at a position close to the stage 14.
[0017]
Laser light emitted from the laser light source 1 is divided by a pair of cylindrical lenses 3, 5, and 4, respectively, in the vertical direction that is the major axis direction and in the horizontal direction that is the minor axis direction. The As a result, this light is converged on the lenses 8, 9, 12, and 13 in one direction as shown in FIG. 8, and the other direction orthogonal to this one direction is shown in FIG. As shown, the lens 7 is stretched in one direction and irradiated onto the substrate 20 to be processed.
[0018]
That is, the substrate 20 to be processed on which a-Si, which is a linear laser beam irradiation object, is formed by linear laser light that is converged in one direction and is elongated in the other direction. Is irradiated.
[0019]
The stage 14 on which the substrate 20 to be processed irradiated with the linear laser beam is moved in the short axis direction of the linear laser beam, that is, the scanning direction. By scanning with such a linear laser beam, large area processing is possible and laser annealing with high throughput is realized.
[0020]
Here, FIG. 2 shows a short line laser beam irradiated to the irradiated object when a diffusion plate is provided between the linear laser beam irradiated object and the condensing lens 13 closest to the irradiated object. The intensity at each position in the axial direction is shown.
[0021]
As shown in the figure, by providing the diffuser plate, it is possible to suppress non-uniformity in particularly strong portions, that is, regions other than the regions a and b at both ends, and the line irradiated to a-si The intensity of the laser beam can be made uniform at any position of the width Ws in the minor axis direction.
[0022]
Therefore, since laser irradiation can be performed sufficiently and uniformly, the crystal grain size of p-Si polycrystallized by irradiation can be sufficiently increased, and a uniform crystal grain size can be obtained. Is no longer present in the membrane.
[0023]
In this way, since the polycrystallization is sufficiently and uniformly performed, a TFT capable of obtaining a sufficient ON current can be obtained. For this reason, in the pixel portion, the ON current of the TFT does not decrease in a part thereof, and a problem such as a decrease in contrast ratio does not occur. Also, in the peripheral drive circuit section, the ON resistance of the TFT increases and the operation speed does not decrease to cause a malfunction. Therefore, even if the number of pixels is increased especially in a large screen, high definition LCD. Further, writing to the pixel can be sufficiently performed, and even if the pulse width in the peripheral driver circuit portion is shortened due to an increase in size or the like, the ON current does not decrease.
[0024]
In the present embodiment, the short axis direction of the linear laser beam has been described. Similarly, in the long axis direction, as shown in FIG. 3, the laser beam irradiated object at each position in the long axis direction. The strength supplied to can be made uniform by providing a diffusion plate. Thereby, as described above, a sufficient and uniform crystal grain size can be obtained.
<Second Embodiment>
Below, the case where a diffusion plate and a slit are arrange | positioned between a to-be-irradiated body and the condensing lens nearest to the to-be-irradiated body is demonstrated.
[0025]
FIG. 4 is a conceptual diagram showing the configuration of the laser beam irradiation apparatus according to the embodiment of the present invention.
[0026]
As shown in the figure, a diffuser plate 40 and a slit 30 are arranged between the irradiated body 20 and the condenser lens 13 closest to the irradiated body.
[0027]
The laser beam that has passed through the condenser lens 13 is covered with the slit 30 as shown in FIG. 6 by covering the regions where the laser beam intensity in the regions a and b at both ends in the major axis direction shown in FIG. The uniform laser light intensity shown can be obtained. Thereby, p-Si having a uniform crystal grain size can be obtained by irradiating a-Si of the irradiated body with the laser beam.
[0028]
Therefore, when it is used for a TFT having the p-si, it is possible to uniformly irradiate a laser beam. Therefore, all the p-Si films formed on the mother glass substrate as the substrate 20 to be processed are Since the TFT made of p-Si has a sufficient ON current in the pixel portion, the number of pixels in a high-definition, large-screen display is small. Even if the writing time to the pixel is increased and sufficient charge supply is possible. In addition, since the drive circuit section also has high response and high speed operation, it is possible to drive with a short pulse width corresponding to a large screen and high definition.
[0029]
The slit 30 is installed at a position sufficiently close to the substrate 20 to be processed. That is, as the slit 30 moves away from the substrate 20 to be processed, the diffraction of the laser light by the slit becomes more prominent, and this diffracted light component prevents the low intensity light component from being generated at the end of the linear laser light in the long axis direction. It is. In the present embodiment, the slit 30 is disposed at a distance of about 30 cm from the substrate 20 to be processed.
[0030]
Furthermore, the slit 30 can be freely adjusted in the length of the linear laser beam in the major axis direction by using a slit whose size is variable. Also in this case, the length can be adjusted according to the dimensions of the mother glass substrate and the TFT substrate size on the mother glass substrate.
[0031]
The diffusion plate 40 can obtain more uniform laser light if it is provided closer to the substrate 20 to be processed than the slit 30.
[0032]
As described above, uniform annealing can be performed on each TFT substrate, and p-Si with high uniform mobility can be obtained.
[0033]
【The invention's effect】
As described above, according to the present invention, the intensity of the laser beam in the minor axis direction and the major axis direction of the linear laser beam can be made sufficiently and uniform, and by supplying it to the irradiated object, it is uniform. It is possible to obtain p-Si with a suitable crystal grain size.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a laser beam irradiation apparatus according to a first embodiment of the present invention.
FIG. 2 is an intensity profile in the minor axis direction of the linear laser beam according to the first embodiment of the present invention.
FIG. 3 is an intensity profile in a major axis direction of the linear laser beam according to the first embodiment of the present invention.
FIG. 4 is a configuration diagram of an optical system of a laser beam irradiation apparatus according to a second embodiment of the present invention.
FIG. 5 is a configuration diagram of an optical system according to a second embodiment of the present invention.
FIG. 6 is an intensity profile in the minor axis direction of the linear laser beam according to the second embodiment of the present invention.
FIG. 7 is a conceptual diagram of a conventional laser beam irradiation apparatus.
FIG. 8 is a configuration diagram of an optical system of a conventional laser beam irradiation apparatus.
FIG. 9 is a configuration diagram of an optical system of a conventional laser beam irradiation apparatus.
FIG. 10 is an intensity profile in the minor axis direction of a conventional linear laser beam.
FIG. 11 is a conventional laser light irradiation diagram.
FIG. 12 is an intensity profile in a major axis direction of a conventional laser beam.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser beam oscillation source 2, 7 Reflection mirror 3, 4, 5, 6 Cylindrical lens 7, 8, 9, 12, 13 Condensing lens 14 Stage 20 Substrate to be processed 30 Slit 40 Diffusing plate

Claims (2)

And the oscillation source of the laser beam,
A plurality of lenses that convert the laser light emitted from the oscillation source into a linear laser light by a combination ;
In the laser beam irradiation apparatus for irradiating the irradiated body with the linear laser beam,
Among the plurality of lenses, between the lens closest to the irradiated body and the irradiated body,
A laser light irradiation apparatus comprising a slit for blocking an end portion of the linear laser light in the long axis direction and a light diffusion plate in this order . The laser beam irradiation apparatus according to claim 1 , wherein the size of the opening of the slit is variable.

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